<template>
    <div>
        <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
            <div class="iconfont header-abs-back">&#xe624;</div>
        </router-link>
        <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
            <router-link to="/">
                <div class="iconfont header-fixed-back">&#xe624;</div>
            </router-link>
            景点详情
        </div>
    </div>
</template>

<script>
export default {
    name:'DetailHeader',
    data () {
        return {
            showAbs:true,
            opacityStyle:{
                opacity:0
            }
        }
    },
    methods:{
        handleScroll () {
            const top = document.documentElement.scrollTop
            if(top>60) {
                let opacity= top / 140
                opacity = opacity>1 ? 1 : opacity
                this.opacityStyle={ opacity }
                this.showAbs=false
            } else {
                this.showAbs=true
            }
        }
    },
    activated () { //当页面显示的时候触发
        window.addEventListener('scroll',this.handleScroll)
    },
    deactivated () { //当页面即将被隐藏的视乎被触发，因为事件是绑定在全局上的，会影响所有组件，需要解绑
        window.removeEventListener('scroll',this.handleScroll)
    }
}
</script>

<style lang="stylus" scoped>
    @import '~style/varibles.styl'

    .header-abs
        position absolute
        top .2rem
        left .2rem
        width .8rem
        height .8rem
        line-height .8rem
        text-align center
        border-radius .4rem
        background rgba(0,0,0,.8)
        .header-abs-back
            color #fff
            font-size .4rem
    .header-fixed
        z-index 2
        position fixed
        top 0
        left 0
        right 0
        height $headerHeight
        line-height $headerHeight
        text-align center
        color #fff
        background $bgColor
        font-size .32rem
        .header-fixed-back
            position absolute
            left 0
            top 0
            width .64rem
            text-align center
            font-size .4rem
            color #fff
</style>
